A study examined students' perceptions of an instructor's use of slang and verbal aggression in giving a presentation. The study used an experiment to investigate the relationship between these two variables and students' perceptions of credibility, affect, and immediacy. Participants, 167 undergraduate communication students at a large midwestern university, attended a research session outside of class and listened to one of four audiotapes of a presentation. The instructor's use of slang and verbal aggression were manipulated in 4 conditions: with verbal aggression only: (39 participants); with slang only (39); with both (45); and, a control condition, with neither (44). After listening to the lecture, participants completed a questionnaire. Results indicated that the instructor's competence was higher in the control condition than in the verbally aggressive and the combination conditions. Participants also reported greater lecture affect for the slang condition over the verbally aggressive and combination conditions. The verbally aggressive condition was rated significantly lower than all three of the other conditions. Findings suggest that, overall, the conditions with verbal aggressiveness were perceived much more negatively than the conditions without verbal aggression. An area for further exploration is the effect of a teacher's use of verbal aggression and slang on cognitive learning. (Contains 1 table of data and 35 references.) (Author/CR)